Abstract:Plasma
aided grafting of 100% cellulosic paper was investigated using atmospheric
pressure plasma generated at audio frequency 4-12 kHz. Atmospheric pressure
plasma is generated by a dielectric barrier discharge operating at 4.8kW audio
frequency power supply. Grafting active chemicals onto cellulosic papers was
conducted using spraying technique either prior or post plasma exposure. The
active exposure area inside the discharge is ~ 60 x 60 cm between two copper
electrodes embedded in Lexan insulators to act as dielectric barrier discharge,
with a fixed 5 cm electrode separation. Helium gas is used as the seed gas
to initiate the discharge and is injected between the electrodes into a test
cell at a constant flow rate of 10L/m. Oxygen was introduced into the
helium flow at a ratio of 1%. Oxygen is used as the surface activation plasma
gas, which allows for scission of the cellulose chain to induce cross-linking of
antimicrobial agents. The discharge has typical parameters of 1-2eV electron
plasma temperature and an electron number density of 1E14 - 1E16 /m^3.

Before and/or after treatment in the plasma the
samples were grafted with active antimicrobial agents, specifically beta-cyclodextrin
or chitosan. Glycidyl Methacrylate, often used as a linker to attach the
chitosan or Beta-cyclodextrin to the polymer chain of the fibers, was also
grafted followed by subsequent grafting of the active agents. Exposure to plasma
was limited to two minutes.

The percent add-on of active agents was
determined by the weight change after preliminary washing. The % add-on of
Glycidyl Methacrylate varies between 4.88 to 6.31%. For other active agents, the
% add-on varies between 3.66 to 10.19%. Scanning Electron Microscopy (SEM)
showed evidence of grafted agents. Fourier Transform Infrared Spectroscopy
(FTIR) showed the typical peaks of grafted active agents.